The present disclosure relates to a starter battery pack for use with outdoor power equipment, such as a snowthrower. More specifically, the present disclosure relates to a self-warming circuit that uses power stored within the starter battery pack to heat the starter battery pack to increase the output, especially at low operating temperatures.
The use of snowthrowers (or snowblowers) by both commercial and residential operators is common for those located in snowy winter climates. These snowthrowers may be walk-behind units or may be propelled by other machinery (e.g., all-terrain vehicles, tractors, etc.). Typically, snowthrowers are divided into two categories: single-stage snowthrowers and multi-stage snowthrowers. Single-stage snowthrowers generally incorporate an impeller assembly that is driven by an internal combustion engine (or similar prime mover, such as an electric motor) to perform the functions of propelling the snowthrower forward, lifting snow from the surface to be cleared, and ejecting the snow out of a discharge chute. Alternatively, a multi-stage snowthrower comprises a separate auger assembly and impeller assembly. Both the auger assembly and impeller assembly are driven by an internal combustion engine (or similar prime mover). The auger assembly rotates near the surface to be cleared in order to lift and direct snow and debris to the impeller assembly, which rotates along an axis perpendicular to the axis of rotation of the auger assembly. The impeller assembly then acts to eject snow out of a discharge chute.
Conventionally, the engines of both single-stage and multi-stage snowthrowers have been started using recoil rope-pull starters. These types of starters require the operator to physically pull a rope to start the engine. In fact, multiple rope pulls are often required before the engine begins to run, particularly during cold weather. Such physical interaction necessary to start the engine is generally undesirable, as some operators may not be capable of using a rope-pull starter even once, let alone multiple times.
As an alternative to rope-pull type starters, some snowthrowers are equipped with electric starter motors that are selectively coupled to a geared flywheel to initiate starting. However, a disadvantage of this type of electric starter system is that it generally requires a 110V corded electric input to provide the electricity to run the starter. This dictates that the operator be near a suitable electrical outlet (and have a suitable electrical cord) at the time of starting if they wish to utilize the electric starter functionality. Given the variety of locations in which snowthrowers are used, this is not always the case.
Accordingly, it would be advantageous to have a snowthrower capable of battery-powered electric starting. Since lead acid batteries suffer from significant disadvantages when not used for extended periods of time or in cold environments, a lithium ion starter battery pack is a contemplated replacement for a 110V corded electric input to provide the electricity to run the starter. Lithium ion starter battery packs can be configured to generate the required high starting current and can be easily recharged. However, the output of a lithium ion starter battery pack significantly decreases as the ambient temperature decreases. Thus, a solution that also increases the output of the starter battery pack at low ambient temperature would be a significant advancement.